Custom LCD gauge cluster

[sfk]

So I've been learning a lot about this stuff over the last few weeks. I'm loving QT. Very powerful. At this stage I am getting to grips with the graphics and event programming side of things. I'd love to make this work but still haven't come to a solid understanding of the hardware side of things. I think these things will become somewhat self evident in time and it will just take exhaustive exploration to find out what will and won't work.

I'm quite set on cheap open source solutions. I know if budget wasn't a constraint you could commission a custom system but this would only work for a specific controlled application.

I have the choice to make soon. Continue with the more limited but easy Nextion display approach or dive into high tech dynamic HD. The development process is worlds apart. The Nextion is basically a pre-programmed display with is triggered by serial commands. All the heavy lifting is done by the display itself. It holds all the graphic elements and can even have its own logic programming. But every change you make requires writing an image to a SD card, then physically inserting the card into the back of the display to flash the device. It's OK but tedious on the bench. Once this is installed though without physical access to the SD card slot your only option is 9600 baud serial...

A video signal generated by a host and simply transferred via HDMI cable would make things SOOO much better.

[Kevin Sharpe]

A video signal generated by a host and simply transferred via HDMI cable would make things SOOO much better.

HDMI interfaces for lots displays are readily available... why is that not an option?

https://www.ebay.ie/itm/3-4-inch-round- ... 4191240944

[sfk]

A video signal generated by a host and simply transferred via HDMI cable would make things SOOO much better.

HDMI interfaces for lots displays are readily available... why is that not an option?

https://www.ebay.ie/itm/3-4-inch-round- ... 4191240944

It's not a problem finding great HDMI display options. The issue is with the hardware to drive them. You can't do it with Arduino, Teensy, ESP32, STM32 microcontrollers. You have to step up to full microprocessors such as the Arm - A core or NXP i.nxp6 with built-in video codec.

These are readily available and priced pretty well. The problem with going to a microprocessor is the move away from ultra fast "bare metal" programming to a full OS (usually a variety of Linux). So the prime example is Raspberry Pi. Just a bit of googling will show how amazing this is, but it takes a bit of time to boot up. There are probably clever ways to speed it up (not loading unneeded stuff, or not ever shutting down completely) but still takes awhile. Unlike the mircrocontrollers which are instantly on.

I've been making rapid progress with Arduino microcontroller development. I still think this is the right approach for tapping into the car's existing wiring loom, watching the electrical signals and generating CAN messaging for signalling the other components.

The dashboard could be driven by an Arduino listening for CAN and outputting to "smart" displays, or could be a RasPi doing similar but generating video graphics "on the fly". The latter being a next level of challenge.

[xp677]

The larger STM32 models can drive HDMI displays through their MIPI-DSI port, FYI.

Boot time of units such as the Raspberry Pi depends on what you're booting. There are examples of people having Pi programs running within a few seconds of startup.

[sfk]

The larger STM32 models can drive HDMI displays through their MIPI-DSI port, FYI.

The specs for this format (mipi-dsi) are very vague. I know that it's a proprietary standard. At least on the Raspberry Pi you can't just plug any mipi-dsi display into the dedicated on-board connector. Only the official screens work.

I don't know if this is the same with other microcontroller boards like STM. But I do know that the resolution is limited, possibly frame rate and colour depth too. And not sure if the odd aspect ratio (3:1) I need is possible either.

Boot time of units such as the Raspberry Pi depends on what you're booting. There are examples of people having Pi programs running within a few seconds of startup.

Yeah I have seen some boot videos on youtube and know it's possible. But with the QT abstraction layers there's always going to be that overhead at least.

I have a Pi 2B laying around so just getting that setup to test. I don't have the wide aspect screen yet, but can use a different screen.

Finally, the version of QT I have been working with is the free version. I can't confirm for sure but I suspect that deploying the QT project to the Raspberry PI platform with Boot 2 QT requires a commercial license. I can't find a definitive answer on the QT website. The instructions and videos I looked at are for an older version of QT and the menus and install has changed. Big sections of the install options tree are missing making me think they're just not included in my version.

Not sure I want to spend $700 / month to find out I'd rather spend $700 on a GS450H transmission.

[sfk]

So I think I answered my own question: "Qt for Device Creation is a product available only under a commercial license"

[Kevin Sharpe]

So I think I answered my own question: "Qt for Device Creation is a product available only under a commercial license"

If you're planning an open source solution then I don't think you have a problem if you're willing to share your code;

https://www.qt.io/download-open-source

[Kevin Sharpe]

Have you considered Renesas R-Car running Qt open source?

https://resources.qt.io/industry-soluti ... r-showcase

https://www.renesas.com/us/en/solutions ... ar-d3.html

https://www.renesas.com/kr/en/support/p ... pport.html

https://elinux.org/R-Car

https://github.com/renesas-rcar

[Kevin Sharpe]

Have you considered Renesas R-Car running Qt open source?

I'd also take a serious look at Automotive Grade Linux (here).

Which could be run on the BeagleBone Enhanced SBC which cost ~75 USD with HDMI interface (here).

Mounted inside a BeagleBone Cape if you want the full IP67 'waterproof' enclosure (here). Also available with extended operating temperature from -40 to +85 deg C.

This would give you a low cost ruggedised platform built on open source (here) which would allow the rest of us to contribute

[sfk]

If you're planning an open source solution then I don't think you have a problem if you're willing to share your code;

https://www.qt.io/download-open-source

No. The open source version doesn't include any device deployment stuff. Only the commercial version. And there is a royalty on every device from what I can tell. It's POA type of license.

I haven't given up on QT yet. I really like it, but would need to find a commercial application for it to persue any further. I think there is a great market for classic car gauge cluster upgrades, not just EV conversions but resto-mods too.

I wouldn't think the JC Cosmo is the right one to develop though. Global market would be 50 units top. But the FD RX7 or Miata... Massive.

[sfk]

Have you considered Renesas R-Car running Qt open source?

Hey thanks for the heads-up. I'll dive in and report back my findings.

Steve